Django-rest-framework学习（－）Serialization

Django-rest-framework学习（－）Serialization

标签（空格分隔）： 互联网 API Django

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前提

Python (2.7, 3.2, 3.3, 3.4, 3.5)
Django (1.7+, 1.8, 1.9)

虚拟环境搭建

    pip install virtualenv
    virtualenv frankstar        //会在当前目录下创建一个目录 即改虚拟环境里所需要的一些资源都会在这个目录下
    cd frankstar
    source ./bin/activate  //进入虚拟环境 
    deactivate   // 退出虚拟环境
    (frankstar) ➜  frankstar

安装相应的一些包

 （1）可以将一些你觉得合适的包放在一个文件中，使用
    pip install -r <filename> 统一安装
  例: requirements.txt
    django == 1.8.0
    djangorestframework
    pygments
    mysql-python == 1.2.5
 （2）当然也可以选择想起一个安装一个这样的方式

正式开始

    django-admin.py startproject tutorial
    cd tutorial
    python manage.py startapp snippets

我们需要将我们的应用snippets和rest-framework 加入到自带的配置文件中INSTALLED_APPS 如下：

    INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'snippets.apps.SnippetsConfig',
    'rest_framework',
)

顺便将数据库的配置也添加进去, 如下：

    DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.mysql',
            'NAME': 'tutorial',
            'USER': 'root',
            'PASSWORD': '',
            'HOST': '127.0.0.1',
            'PORT': '3306',
        }
    }

创建模型

# coding:utf-8
from django.db import models
from pygments.lexers import get_all_lexers
from pygments.styles import get_all_styles


LEXERS = [item for item in get_all_lexers() if item[1]]
LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in LEXERS])
STYLE_CHOICES = sorted((item, item) for item in get_all_styles())


class Snippet(models.Model):
    """docstring for Snippet"""
    # 定义该模型的字段及相应的类型
    created = models.DateTimeField(auto_now_add=True)
    title = models.CharField(max_length=100, blank=True, default='')
    code = models.TextField()
    linenos = models.BooleanField(default=False)
    language = models.CharField(choices=LANGUAGE_CHOICES, default='python', max_length=100)
    style = models.CharField(choices=STYLE_CHOICES, default='friendly', max_length=100)

    class Meta:
        ordering = ('created',)

执行以下命令：

    python manage.py makemigrations snippets //创建模型snippets
    python manage.py migrate   //将模型转化为数据库表存到数据库中

创建serializer类

在提供web API时，我们常常需要将我们的实例对象转换为相应的数据格式，序列化或者反序列化。Django框架中其实带有了这个功能的库，我们先手试着动创建一个这样的类。
在snippets文件夹下创建一个文件serializers.py,其中定义如下：

#coding:utf-8

from rest_framework import serializers
from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES

class SnippetSerializer(serializers.Serializer):
    """docstring for SnippetSerializer"""
    pk = serializers.IntegerField(read_only=True)
    title = serializers.CharField(required=False, allow_blank=True, max_length=100)
    code = serializers.CharField(style={'base_template': 'textarea.html'})
    linenos = serializers.BooleanField(required=False)
    language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default='python')
    style = serializers.ChoiceField(choices=STYLE_CHOICES, default='friendly')

    def create(self, validated_data):
        '''
         通过给定的有效数据创建并返回一个Snippet对象
        '''
        return Snippet.objects.create(**validated_data)

    def update(self, instance, validated_data):
        '''
        通过给定的有效数据更新并返回一个Snippet对象
        '''
        instance.title = validated_data.get('title', instance.title)
        instance.code = validated_data.get('code', instance.code)
        instance.linenos = validated_data.get('linenos', instance.linenos)
        instance.language = validated_data.get('language', instance.language)
        instance.style = validated_data.get('style', instance.style)

        instance.save()
        return instance

打开Django的shell,试着创建几个Snippet实例

    python manage.py shell

    from snippets.models import Snippet
    from snippets.serializers import SnippetSerializer
    from rest_framework.renderers import JSONRenderer
    from rest_framework.parsers import JSONParser

    snippet = Snippet(code='foo = "bar"\n')
    snippet.save()

    snippet = Snippet(code='print "hello, world"\n')
    snippet.save()

接着调用为这个类创建的序列化类SnippetSerializer,输出json对象

    serializer = SnippetSerializer(snippet)
    serializer.data
    #output: {'style': 'friendly', 'code': u'print "hello,world"\n', 'language': 'python', 'title': u'', 'linenos': False, 'pk': 2}

    content = JSONRenderer().render(serializer.data)
    content
    #output: '{"pk":2,"title":"","code":"print \\"hello,world\\"\\n","linenos":false,"language":"python","style":"friendly"}'

反序列化

反序列化也是类似的处理，紧接着上述的步骤，还是在Django shell中处理

    from django.utils.six import BytesIO

    stream = BytesIO(content)
    data = JSONParser.parse(stream)
    serializer = SnippetSerializer(data=data)
    serializer.is_valid()  //判断是否是有效的json对象
    #output: True

    serializer.validate_data
    #output: OrderedDict([(u'title', u''), (u'code', u'print "hello,world"'), (u'linenos', False), (u'language', 'python'), (u'style', 'friendly')])

    serializer.save()
    #output: <Snippet: Snippet object>

我们可以同时处理多个Snippet实例,只需要在它的构造方法中加入many=True这个参数即可,如下：

    serializer = SnippetSerializer(Snippet.objects.all(), many=True)
    serializer.data
    #output: [OrderedDict([('pk', 1), ('title', u''), ('code', u'foo = "bar"\n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')]), OrderedDict([('pk', 2), ('title', u''), ('code', u'print "hello,world"\n'), ('linenos', False), ('language', 'python'), ('style', 'friendly')]), OrderedDict([('pk', 3), ('title', u''), ('code', u'print "hello,world"'), ('linenos', False), ('language', 'python'), ('style', 'friendly')])]

使用内置的模型序列类ModelSerializers

打开serializer.py,找到SnippetSerializer类定义的地方(create()与update()方法暂时不需要改动),改成如下代码：

    class SnippetSerializer(serializers.ModelSerializer):
    """docstring for SnippetSerializer"""
   # 此处添加你所需要序列化元类的模型和相应的字段
        class Meta:
            model = Snippet
            fields = ('id', 'title', 'code', 'linenos', 'language', 'style')

打开django manage.py shell输入以下命令

    from snippets.serializers import SnippetSerializer

    serializer = SnippetSerializer()
    print(repr(serializer))
    #output: SnippetSerializer():
    id = IntegerField(label='ID', read_only=True)
    title = CharField(allow_blank=True, max_length=100, required=False)
    code = CharField(style={'base_template': 'textarea.html'})
    linenos = BooleanField(required=False)
    ...

使用serializer与views结合

首先在snippets文件下新建一个文件views.py,创建如下代码：

    #coding:utf-8
    from django.shortcuts import render
    from django.views.decorators.csrf import csrf_exempt
    from django.http import HttpResponse
    from rest_framework.renderers import JSONRenderer
    from rest_framework.parsers import JSONParser
    from snippets.models import Snippet
    from snippets.serializers import SnippetSerializer
    # Create your views here.

    class JSONResponse(HttpResponse):
        """docstring for JSONRenderer"""
        '''
        将HttpResponse对象相应的内容转化为json
        '''
        def __init__(self, data, **kwargs):
            content = JSONRenderer().render(data)
            kwargs['content_type'] = 'application/json'
            super(JSONResponse, self).__init__(content, **kwargs)


    @csrf_exempt
    def snippet_list(request):
        '''
        显示所有的snippets的对象,或者创建一个新的对象
        '''
        if request.method == 'GET':
            snippets = Snippet.objects.all()
            serializers = SnippetSerializer(snippets, many=True)

            return JSONResponse(serializers.data)

        elif request.method == 'POST':
            data = JSONParser().parse(request)
            serializers = SnippetSerializer(data=data)
            if serializers.is_valid():
                serializers.save()

                return JSONResponse(serializers.data, status=201)
            return JSONResponse(serializers.errors, status=400)

    @csrf_exempt
    def snippet_detail(request, pk):
        '''
        查找、更新或者删除一个snippet
        '''
        try:
            snippet = Snippet.objects.get(pk=pk)
        except Snippet.DoesNotExist:

            return HttpResponse(status=404)

        if request.method == 'GET':
            serializer = SnippetSerializer(snippet)

            return JSONResponse(serializer.data)

        elif request.method == 'PUT':
            data = JSONParser().parse(request)
            serializer = SnippetSerializer(snippet, data=data)
            if serializer.is_valid():
                serializer.save()

                return JSONResponse(serializer.data)
            return JSONResponse(serializer.errors, status=400)

        elif request.method == 'DELETE':
            snippet.delete()

            return HttpResponse(status=204)

然后在该文件夹(snippets)下再添加一个文件urls.py,部署访问路由：

    #coding:utf-8
    from django.conf.urls import url
    from snippets import views

    urlpatterns = [
        url(r'^snippets/$', views.snippet_list),
        url(r'^snippets/(?P<pk>[0-9]+)/$', views.snippet_detail),
    ]

最后再将改路由文件添加到总路由文件中,如下:

    from django.conf.urls import include, url
    from django.contrib import admin

    urlpatterns = [
        # Examples:
        # url(r'^$', 'tutorial.views.home', name='home'),
        # url(r'^blog/', include('blog.urls')),

        url(r'^admin/', include(admin.site.urls)),

        url(r'^', include('snippets.urls')), #将其包含进来即可
    ]

打开命令行,输入python manage.py runserver,浏览器中输入：http://127.0.0.1:8000/snippets/, 输出如下：

[
    {
        id: 1,
        title: "",
        code: "foo = "bar" ",
        linenos: false,
        language: "python",
        style: "friendly"
    },
    {
        id: 2,
        title: "",
        code: "print "hello,world" ",
        linenos: false,
        language: "python",
        style: "friendly"
    },
    {
        id: 3,
        title: "",
        code: "print "hello,world"",
        linenos: false,
        language: "python",
        style: "friendly"
    }
]

输入某个具体的ID，还可以显示某条具体的内容如：http://127.0.0.1:8000/snippets/2/,输出如下：

    {
        id: 2,
        title: "",
        code: "print "hello,world" ",
        linenos: false,
        language: "python",
        style: "friendly"
    }

总结

这个案例可以从官网上找到,这只是其中一个部分，算是开个头，后续的会不定期的补上，可能细心的人会发现在snippet_list和snippet_detail接口定义中,会有PUT,DELETE,GET,POST等Http方法,但是相应路由只有相应的一条记录，这其中涉及到restful-api的一些知识。虽是同一条路由，但是调用的Http方法不同，相应自然不会相同。